In the related art, there is provided a vehicle equipped with a suspension that includes air springs using compressed air and the like. There is also a vehicle equipped with a vehicle height adjustment apparatus using the air springs. There is a so-called closed type vehicle height adjustment apparatus. This type of vehicle height adjustment apparatus increases a vehicle height by supplying high-pressure air stored in a pressure tank to the air springs that change a suspension state of each wheel. The vehicle height adjustment apparatus decreases the vehicle height by discharging the high-pressure air from the air springs and returning the high-pressure air back to the pressure tank. Among the closed type vehicle height adjustment apparatuses, there is a vehicle height adjustment apparatus that uses a pressure difference so as to supply high-pressure air from the pressure tank to the air springs. There is a vehicle height adjustment apparatus that continuously supplies air to the air springs by driving a compressor to pressure-feed air when supply efficiency decreases during the supply of air by a pressure difference. JP 2001-246919A (Reference 1) is an example of the related art.
An automotive engineer designs a vehicle while always keeping in mind the efficiency of design via the use of common components. Even in designing the vehicle height adjustment apparatus, the automotive engineer seeks to use components used for other purposes in the related art, so as to realize the control and operation of the vehicle height adjustment apparatus.